Electrostatic recorder employing signal switching using a conducting fluid



Jan. T3, 197 R. A. ADAMS ET AL 3,489,850

ELECTROSTATIC RECORDER EMPLOYING SIGNAL swmcrmre USING A CONDUCTING FLUID Filed Jan. 21, 1966 26 soweca OF eouwca OF HIGH VOLTAGE CONDOOTTVE FLwD VIDEO SIGNAL5 UNDER PREssuFzE SOURCE OF A C aOLAQC/E OF COMDU TEVE FLLMD UNDER PRE$$URE 'rHGH VOLTAGE DRWE V\DEO SlGNALS MOTOR A: INVENTORS PM) CAT TNNER o/wA/ A. ADAMS CH CO GEO/P6; H. J'N/(M/SOA A FOR/V5) United States Patent 3,489,850 ELECTROSTATIC RECORDER EMPLOYING SIGNAL SWITCHING USING A CONDUCT- ING FLUID Roman A. Adams, Skokie, and George H. Jenklnson, Glenview, Ill., assignors to The A. B. Dick Company, Chicago, Ill., a corporation of Illinois Filed Jan. 21, 1966, Ser. No. 522,130 Int. Cl. H04n 5/76 U.S. Cl. 178---6.6 2 Claims ABSTRACT OF THE DISCLOSURE An electrostatic facsimile recorder in which a jet of conducting fluid is used to intermittently establish conduction between the video signal source and the writing electrodes.

This invention relates to electrostatic printing systems of the type wherein an electrostatic charge image is deposited on paper and subsequently developed, and more particularly to improvements therein.

One of the techniques employed for performing electrostatic writing is to apply a potential to a moving wire stylus or to selected ones of a plurality of stationary stylii in order to establish an electrostatic charge image on the writing medium with which the stylus is brought in contact. While the amplitude of the voltage which must be established between the stylus and a backing plate in order to obtain the necessary discharge, varies with materials being written on and the spacings involved, the minimum threshold is normally on the order of several hundred volts. The operating of switching several hundred volts with the required speed, and maintaining the required safety precautions necessitates the use of costly components. Insulation break down occurs as well as unwanted discharges and this type of equipment requires continuous maintenance.

One object of this invention is the provision of the novel structural arrangement for affording electrostatic printing.

Yet another object of the present invention is the provision of a unique switch structural arrangement suitable for use in an electrostatic printing system.

Still another object of this invention is the provision of a novel arrangement for switching high voltages which requires a minimum of maintenance.

These and other objects of the present invention are achieved by the use of a switching system in an electrostatic printing system which employs a conductive stream of fluid for establishing a connection with a contact whereby a path between a source of potential and an electrostatic writing stylii is closed. Connection between the conductive fluid and the contact may be made selective by the establishment of relative motion between the two.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawings, in which:

FIGURE 1 is a schematic drawing of an electrostatic writing system in accordance with this invention; and

FIGURE 2 is another schematic arrangement illustrating an electrostatic writing system employing another embodiment of the invention.

Referring now to FIGURE 1, there may be seen, in schematic form, an arrangement for an electrostatic printing system which employs an embodiment of the inven- ICC tion. By way of illustration, and not to be construed as a limitation upon the invention, the arrangement shown in FIGURE 1 illustrates the invention being used in a facsimile-type of recording system. A rotating cylinder 10 has the copy 12 upon which it is desired that a received image is electrostatically deposited on he copy 12, it is grounded. A drive motor 14 rotates the cylinder in synchronism with a cylinder at the transmitter (not shown). Also, a lead screw 16 has a traveling nut 18 mounted thereon, to travel along the lead screw as it is rotated. The lead screws is supported rotatably at both ends by supports 20, 22. The lead screw may be driven from the motor 14 in synchronism with the scanning of the copy which is being scanned at the transmitter.

The lead screw 18 holds an electrostatic writing stylus 24 and accordingly this stylus will move with the lead screw 18 over the paper 12 so that the motion of the lead screw together with the rotation of the drum 10 will result in a complete coverage of the copy .12. After an image is electrostatically deposited on the copy 12, it is removed from the drum and fixed, using well-known xerographic techniques, by sprinkling toner powder thereover or by passing it through a liquid developing solution.

The signals which are applied to the stylus 24 are received from a high voltage video signal source 26, which is representative of the front end of a facsimile receiver which receives the video signals which are transmitted and converts them into voltages of sufiicient amplitude to exceed the threshold voltage required for electrostatic printing. The output of the high voltage video signal source is applied to a vibrating contact 28. This comprises a base plate 28A upon which there is attached a solenoid coil 288. A flexible plate 28C is supported over the solenoid coil 28B at one end thereof by a supporting block 28D. A contact rod 28E is attached to the end of the flexible plate 28C. A source of alternating current 30 is connected to the solenoid coil 28B. It will be appreciated that when the source of alternating current energizes the solenoid 28B, the flexible plate 28C is caused to oscillate whereby the contact rod 28E vibrates between the two positions illustrated by the dotted lines adjacent thereto.

A conductive fluid source 32, which is under pressure, is applied to a nozzle 34, which is positioned to direct the conductive fluid which flows therethrough at one position of the rod contact 28E during its oscillation. The conductive fluid may be any suitable fluid, such as salt water or a mixture of oil and carbon particles, etc. The fluid is caught after discharge from the nozzle 34 in a fluid catch container 36. This container output is then fed to a pump 38, which pumps it back under pressure to the source 32.

The nozzle 34, which may be made of any suitable metal pipe, is connected to the stylus 24. Accordingly, a voltage applied by the video signal source 26 to the rod contact 28E is connected by the conductive fluid stream 40 emitted by the nozzle 34 and striking the rod contact 28E, to the stylus 24. The source of alternating current 30 will cause the rod contact 28E to move into and out of contact with the conductive fluid stream at a rate which may be controlled and which may be operated synchronously if desired. In any event, the vibration of the contact 28E chops the video signal and establishes an electrostatic image pattern as a sequence of dots whose spacing and number are easily controlled by varying the frequency of oscillation of the vibrator 28.

FIGURE 2 is a schematic diagram of an embodiment of the invention wherein the contacts are stationary and the nozzle, which directs the conductive fluid jet, is movable. A source of conductive fluid under pressure 42 connects through a pipe 44 to a rotary pipe coupling joint 46 which is rotatably driven by a drive motor 48. Another 3 pipe 50 is carried by the rotary pipe coupling joint 46 to rotate therewith. The joint 46 simply consists of a hous ing which is rotatably coupled to the stationary pipe 44 at one side and from the opposite side of which the pipe 50 fixedly coupled to it extends.

The pipe 50 extends to the nozzle section 52 which rotates therewith. The conductive fluid jet 54 is emitted from the nozzle and traverses a rotary path. Positioned at spaced intervals in a circle around the rotatin pipe 50, at a distance from the nozzle 52 so that the jet 54 will successively strike each one of them before it breaks up, are a plurality of contacts 56. Each one of these contacts is supported to be insulated from the adjacent contacts. The spaces between the contacts are left open so that no fluid can bridge these spaces. Each one of these contacts is connected by a lead 58, to a separate stylus 60. These stylii terminate on a moving web 62 of paper. Paper comes olf of a pay ofl roll 64, passes through a developing and fixing box 66 wherein toner powder is deposited on the electrostatic image and then fused to the paper, and is thereafter taken up on a take up roller 68. A ground plate 70 is placed on the back side of the web opposite the stylii 60.

A source of high voltage video signals 72 is connected to the pipe which is connected to the nozzle 52. When the nozzle completes one rotation it has applied, via the conductive jet 54, one line of video signals to the respective stylii 60. Provision for synchronizing the rotation of the nozzle with the scanning video signal source at the transmitter (not shown) may be made in a well-known manner by applying video line synchronizing signals to the drive motor 48 so that it will rotate the nozzle in synchronism with these line signals. If a retrace interval is required so that the scanner at the transmitter can go from the end of one line to the beginning of another line of video, this may be effectuated by leaving a space between the two contacts 56 which are associated with their stylii which write at the end of the line and at the beginning of the next line. A fluid catch container 74 is positioned underneath the contacts 56 to receive the conductive fluid which runs down the contacts as well as the conductive fluid stream which passes through the space between the contacts.

The stylii 60 will deposit a line of charges on the paper 62 in response to the video signals. The paper is moved at a speed which is in synchronism with the horizontal scanning speed employed at the transmitter (not shown). In this manner, an image is drawn which is developed by the developing and fixing box 66 which either cascades dry toner powder on the paper or can use a wet developing system.

There has been accordingly described and shown herein a novel, useful and unique arrangement for an electrostatic printing system which uses a conductive fluid jet for applying video voltage signals to stylii to effectuate electrostatic printing. The arrangement provides switching 4 of signals without the wearing of contacts, provides switching of signals without contact bounce, and needs substantially no maintenance.

What is claimed is:

1. In electrostatic apparatus a source of video signals, a stylus for depositing electrostatic charges responsive to said signals from said source, and means for coupling signals from said source to said stylus including a source of conductive fluid under pressure, a conductive nozzle coupled to said source of conductive fluid under pressure to emit a conductive fluid jet from an end of said nozzle, a connection between said nozzle and said stylus, a conductive rod connected to said video signal source, and means for vibrating said rod through a path which cuts through said conductive fluid jet.

2. In an electrostatic printing system, a source of video signals and a plurality of electrostatic stylii for producing electrostatic charge deposition responsive to signals from said source of video signals, means for selectively connecting said video signal source to said plurality of stylii including a plurality of contacts spaced from One another in a manner to describe a circle, a conductive fluid jet positioned at the center of said circle, means for rotating said fluid jet to enable it to successively come in Contact with each one of said contacts including a source of conductive fluid under pressure, a rotatable pipe coupling joint, first pipe means for coupling said source of fluid under pressure to said rotatable pipe coupling joint, a nozzle coupled to said rotatable pipe coupling joint to be rotatable therewith, and motor means for rotating said rotatable pipe coupling joint whereby fluid from said source of conductive fluid under pressure flows out of said nozzle to form a fluid jet and is rotated with said nozzle, and means for connecting said source of video signals to said conductive fluid jet.

References Cited UNITED STATES PATENTS 1,198,270 9/1916 Poulsen 346-75 2,640,890 6/1'953 Johnson 200l52 3,022,401 2/ 1962 Wilkerson 335-51 3,230,303 1/1966 Macovski et a1.

3,308,473 3/ 1967 Sawazaki.

OTHER REFERENCES Rotary-Jet Merucury Switching Technique (received US. Patent Oflice Nov. 23, 1960).

US. Naval Electronics Laboratory, San Diego, Calif., NEO51334 Report 297 (p. 3);

RICHARD MURRAY, Primary Examiner DONALD E. STOUT, Assistant Examiner US. Cl. X.R. 34674 

